EP0882561A1 - Method of manufacturing a sound damping panel - Google Patents

Abstract

The acoustic insulation panel is a solid polyurethane plate on a foam base, moulded at a low pressure. Also claimed is a mould with a lower die (4) and an upper die for moulding the solid polyurethane plate and a second upper die to mould the foam support.

Description

The present invention relates to a method for producing a soundproofing panel, and more particularly such a process in which combines a massive plate with a foam support.

Such panels are known, for example, in the industry automobile where they are used to isolate the passenger compartment from the environment outside. Inside the passenger compartment, they can be in the form of mat to isolate occupants from noise caused by rolling vehicle on the road. We also have it behind the board edge to attenuate the noise caused by the engine and the gearbox.

These panels are currently produced in the form of a plate massive high density plastic generally called heavy mass, or septum, associated with a foam support. This together behaves with respect to the vibrations of the metal floor of the passenger compartment or bulkhead separating this passenger compartment from the engine compartment, like a spring, the foam, associated with a part of inertia, the plate massive. This results in vibration damping and therefore an effect of noise reduction.

So far, the massive plates have been made from a blank of thermoplastic material loaded with a density of the order of 1.7 to 2.4, this density being relatively variable. This blank is shaped by a thermoforming process in which it is heated and then vacuumed in a mold.

This process has a number of drawbacks.

First, it is inherent in thermoforming processes by vacuum suction lead to the production of peripheral falls to the piece produced. This sometimes results in material losses.

Furthermore, the thermoplastic materials used are of a family of plastics different from that of foam. During recycling, it it is therefore necessary to separate the latter from the massive plate, which increases recycling costs.

Another disadvantage is that the materials thermoplastics used are very viscous. We are therefore brought to use plasticizers. However, these have the characteristic of being spray, when brought to a relatively high temperature such than that which may prevail in an exposed motor vehicle interior under the sun. This vaporized plasticizer then tends to condense on the windows and to produce the phenomenon called "fogging", producing a certain clouding of the passenger compartment windows.

In addition, the thermoplastic blanks used so far are made by high pressure injection, which is known to be a process expensive.

Another disadvantage of the known method lies in the fact that the blank of thermoplastic material used for the production of the solid plate, is of constant thickness. It is therefore impossible to control the thickness of the final product. When the latter is relatively flat, its thickness will be, also relatively constant. On the other hand, when we impose on the blank deformations leading to significant depressions, the thickness of the part final will be greatly reduced in the hollow parts.

Finally, given the high cost of the raw material used for make these thermoplastic blanks, we use recycled products leading to blanks whose homogeneity and reproducibility of properties, especially mechanical, is relatively low.

The present invention aims to overcome these drawbacks.

To this end, the invention firstly relates to a method for the production of a soundproofing panel, in particular for a passenger compartment in a vehicle automobile, in which a massive plate is associated with a support in foam, characterized in that said massive plate is made of filled polyurethane molded at low pressure in a mold having the form said panel.

This results in the first place in saving material, since such a process obviously does not lead to the production of peripheral falls to the molded part.

In addition, polyurethane belongs to the same family as foam. This results in better recyclability of the soundproofing panel, without the need for separation of its components.

In addition, the viscosity of polyurethanes being low, it is not necessary to use plasticizers, which eliminates the problem of "fogging".

The implementation costs are also reduced since the polyurethane plate can be molded at low pressure.

Another advantage of the invention lies in the fact that the thickness of the massive plate is perfectly controlled. It results, in fact, only of the air gap between the different parts of the mold and is, in particular, independent of the forms to be obtained.

The soundproofing panel obtained also has the advantage of being relatively flexible. Its installation and removal are facilitated.

Finally, the molded polyurethane plate is not obtained from recycled materials. The result is much more homogeneous products including the characteristics, in particular the density, are precisely determined.

In a first embodiment, it is sprayed separately into the molds filler and polyurethane. This spraying is thus carried out at from two nozzles, and is then preferably carried out at a fixed point in the mold. This solution is therefore particularly suitable for carrying out relatively small parts.

In another embodiment, the load and the mixture are mixed. polyurethane in a spray head, and the mixture is sprayed into the mold. The spray head can then be movable, so as to distribute at will in the mold the mixture of polyurethane and filler. This solution is therefore more particularly suited to the production of large dimension.

The spray head (s) can in any case be fixed or mobile regardless of whether the mixing is carried out before or during spraying.

In a particular embodiment, the plastic material to foam is poured directly on the massive plate, in the same mold where it was carried out, the foaming being carried out in this mold after setting place of a new suitable punch.

Thanks to such an embodiment, it is possible to obtain high production rates and reduce investment related to mold making.

The invention also relates to a mold for the production of a soundproofing panel in which a solid plate is associated with a foam support, characterized in that it comprises a matrix and a first punch whose air gap is arranged for molding a plate massive filled polyurethane, and a second punch arranged to define with said massive plate held in said matrix, a volume for foaming a suitable material.

The subject of the invention is also a soundproofing panel, characterized by the fact that it is produced by a process as described above.

More particularly, functional members can be molded in one piece with the massive plate.

This simplifies the manufacture of the panels, by eliminating assembly operations of members such as inserts or clips. We'll see also that the acoustic properties of the panel are thus improved.

• Les figures 1a à 1d illustrent quatre phases d'un procédé selon l'invention;
• la figure 2 est une vue en coupe du panneau insonorisant obtenu par ce procédé;
• la figure 3 est une vue en coupe d'un tel panneau insonorisant muni d'une agrafe de câblage;
• la figure 4 est une vue en coupe d'un autre panneau insonorisant muni d'un élément de fixation; et
• la figure 5 est également une vue en coupe d'un panneau insonorisant selon l'invention comportant localement une surépaisseur.

A particular embodiment of the invention will now be described, by way of nonlimiting example, with reference to the appended schematic drawings in which:

• Figures 1a to 1d illustrate four phases of a method according to the invention;
• Figure 2 is a sectional view of the soundproofing panel obtained by this method;
• Figure 3 is a sectional view of such a soundproofing panel provided with a wiring clip;
• Figure 4 is a sectional view of another soundproofing panel provided with a fastening element; and
• Figure 5 is also a sectional view of a soundproofing panel according to the invention locally including an additional thickness.

The method according to the invention generally comprises two main steps. The step of Figures 1a and 1b is that where the heavy mass 2 of panel 1, and the step of FIGS. 1c and 1d is that where made the foam 3 of this panel.

The first phase of the first step is shown in Figure 1a. During this phase, the bottom of the die 4 of a mold is filled with a mixture of polyurethane and a filler. In this case, the polyurethane is delivered from a nozzle 5, and the charge from a nozzle 6, which can be fixed in particular in the case of a low mold dimension, or movable. It will be observed that the mixture of polyurethane and the charge is made in the mold itself, but we could alternatively make this mixture beforehand and spray it using a single nozzle.

The second phase of the first stage, represented in FIG. 1b, consists in closing the mold by covering the matrix 4 with a first punch 7. The mixture of polyurethane and filler is thus compressed at low pressure to form the heavy mass 2.

We note that this process allows to control at will the thickness of this heavy mass. For example, here it forms a rib 8 corresponding to a groove 9 made in the matrix 4. Of course, extra thicknesses such as groove 8 could also be formed of the other side of the heavy mass 2, by making indentations in the hallmark 7. In the latter case, the extra thicknesses would be included in the foam 3.

After molding the heavy mass 2, the punch 7 is removed and replaced on die 4 by a second punch 10. As shown in Figure 1c, the punch 10 household above the heavy mass 2, a volume foaming 11 communicating with a supply channel 12.

As shown in Figure 1d, plastic is then injected into volume 11 through channel 12, and this plastic material forms in volume 11 the foam 3.

It will be noted that the thickness of the foam 3 can be controlled by same as that of the heavy mass 2. The foam 3 forms here a recess 13 due to a part 14 of the punch 10 projecting into the volume foaming 11.

After foaming of the plastic and formation of the foam 3, the soundproofing panel 1 of FIG. 2 is ejected from the mold.

The invention therefore makes it possible to form panels soundproofing including, among other advantages, the thickness of the heavy mass can be perfectly controlled. We will now see that the result possibility of integrating functions into the heavy mass which, in the prior art, had to be fulfilled by reported bodies.

FIG. 3 shows how a staple 20 can be produced in a single piece with the heavy mass 21. This clip 20, intended here for the holding a cable 22, is formed by two projections 23 and 24 extending from a reinforced zone 25 of the heavy mass 21. This thus avoids the use of a separate staple, metallic or plastic, itself clipped into an opening in the soundproofing panel.

In FIG. 4, a clip or a fixing insert of the prior art is replaced by a block 26 molded in one piece with the heavy mass 27. Block 26 passes entirely through the soundproofing panel and has, on the foam, a hole 28 replacing that of the clip or insert for fixing the sign.

It will be observed that, in the two embodiments which come to be described, the invention has an additional advantage. Indeed, we eliminates the need encountered in the prior art to provide orifices in the soundproof panel. This results in better insulation phonic.

FIG. 6 illustrates another application of the invention, in which the panel shown is an apron insulating panel. Here the heavy mass 29 has along its edge an extra thickness 30 made of a single play with it. This extra thickness in this case replaces an insert which, in the prior art, is partially embedded in the foam of the panel.

Claims (9)

Method for producing a soundproofing panel (1), especially for the passenger compartment of a motor vehicle, in which one associates a massive plate (2) to a foam support (3), characterized by the fact that said massive plate is made of polyurethane filled molded to low pressure in a mold having the shape of said panel. Method according to claim 1, in which the spray is sprayed separately in the mold the filler and the polyurethane. Method according to claim 1, in which the charge is mixed and the polyurethane in a spray head, and the mixture is sprayed in the mold. Method according to any one of claims 1 to 3, in which is sprayed polyurethane from a fixed point. Method according to any one of claims 1 to 3, in which is sprayed polyurethane from a movable head. Process according to any one of Claims 1 to 5, in which the plastic to be foamed is poured directly onto the plate massive (2), in the same mold where it was made, foaming (11) being produced in this mold after placing a new punch (10) adapted. Mold for the production of a soundproofing panel in which a massive plate (2) is associated with a foam support (3), characterized by the fact that it comprises a matrix (4) and a first punch (7) whose air gap is designed for molding a solid polyurethane plate (2) loaded, and a second punch (10) arranged to delimit with said massive plate held in said matrix, a volume for foaming of an appropriate material. Soundproofing panel, in particular for vehicle interior automobile, characterized in that it is produced by a method according to one any of claims 1 to 6. The sound absorbing panel of claim 8, wherein functional members (20; 26; 30) are molded in one piece with said massive plate.

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